1. Field of the Invention
The present invention relates to an electrophotographic photoreceptor, a process cartridge and an electrophotographic photoreceptor manufacturing method (hereunder sometimes called simply a “photoreceptor” and a “manufacturing method”), and specifically relates to an electrophotographic photoreceptor and a process cartridge for use in various kinds of electrophotographic devices such as copiers and printers, and also relates to a method for manufacturing an electrophotographic photoreceptor.
2. Description of the Related Art
In recent years, organic electrophotographic photoreceptors (organic photoreceptors) provided with a functional layer of an organic material on a support have come to predominate as electrophotographic photoreceptors. This is because of the diversity of material design for organic semiconductors, which has led to the development of superior charge generating materials, charge transport materials and binder resins, and allowed the production of low-cost, high performance commercial photoreceptor products. These organic photoreceptors can be classified generally into functionally separated semiconductors comprising a charge generating layer stacked with a charge transport layer, and monolayer photoreceptors comprising a charge generating material and a charge transport material dispersed in a single layer.
Electrophotographic photoreceptors are subjected to repeated cycles of charging, exposure, development, transfer, cleaning and charge neutralization during the image forming process. This image forming process comprises a sequence of processes, specifically charging the surface of the photoreceptor, forming an electrostatic latent image by light exposure on the surface of the photoreceptor, developing this electrostatic latent image with toner, transferring the formed toner image to a transfer medium, removing the residual toner on the photoreceptor surface with a cleaning blade, and neutralizing the charge on the photoreceptor surface.
The cleaning step of removing residual toner from the photoreceptor surface after the transfer step is particularly important for obtaining a clear image. One cleaning method used in this process is a method of scraping off the residual toner by pressing an elastic cleaning blade against the photoreceptor surface. However, the problem has been that because there is normally a large frictional force operating between the elastic blade and the photoreceptor surface, the elastic blade is liable to curl back, particularly at the beginning of use when the photoreceptor and elastic blade have not become adjusted to each other.
Conventionally, one method that has been proposed for solving this problem is to roughen the photoreceptor surface to a suitable degree to reduce the contact area between the photoreceptor surface and the elastic blade and thereby reduce the frictional force. Because the problem of friction between the elastic blade and the photoreceptor is normally greater the higher the mechanical strength of the photoreceptor surface and more resistant the outside of the photoreceptor is to wear, roughening the photoreceptor surface is an extremely effective way of alleviating the problems that occur when the photoreceptor surface is strengthened by improving the resin making up the surface layer of the photoreceptor.
Specific methods of roughening the photoreceptor surface include the following. For example, JP-A-H4-281461 (Claims, etc.) discloses a technique using a layer of metal or metal oxide fine powder dispersed in a binder resin as a surface protective layer of an electrophotographic photoreceptor. JP-A-S57-094772 (Claims, etc.) discloses a method for polishing the surface of an organic electrophotographic photoreceptor, in which the photoreceptor surface is polished with a specific metal wire or fiber brush to thereby form fine projections and indentations on the surface of the photoreceptor. JP-A-H2-139566 (Claims, etc.) discloses a technique for roughening the surface of an organic electrophotographic photoreceptor by using a film abrasive to grind the photoreceptor in at least two directions at different angles to the direction of a generatrix.
These conventional techniques are thought to be somewhat effective because they roughen the photoreceptor surface to a certain degree. However, techniques have yet to be established for fabricating the surface form of the photoreceptor with finer and more precise control in order to improve the performance and productivity of the photoreceptor.
There have also been proposals for more detailed analysis and research focused on controlling the surface forms of photoreceptors, and for example WO 2005/093518 (Claims, etc.) proposes an electrophotographic photoreceptor provided on the circumference with multiple dimple-shaped recesses so as to resolve problems with the cleaning properties, rubbing memory and the like. However, with this technique it is thought that improvements in durability will be required to extend the life of the photoreceptor.
JP-A-2001-066814 (Claims, etc.) discloses a technique for forming specific projections and indentations on the outermost surface of an electrophotographic photoreceptor by using a touch roll with surface projections and indentations to mold the outermost surface of the photoreceptor. With this technique, however, it is thought that the initially formed projections and indentations will not be maintained over use because the surface layer of the photoreceptor is composed of a thermoplastic resin.
Furthermore, JP-A-H6-282089 (Claims, etc.) discloses a photoreceptor comprising grooves of a specific width and depth in parallel in the circumferential direction on the surface of a cylindrical base body, wherein the cross-section of each groove has a regular shape in the direction of width, thereby regularly changing the film thickness of a coating layer. JP-A-2000-227671 (Claims, etc.) discloses an organic photoreceptor comprising surface roughness waveforms formed regularly on the surface of a substrate, and having fine projections and indentations of a specific height within each waveform of these regular surface roughness waveforms. JP-A-H8-123058 (Claims, etc.) discloses an electrophotographic photoreceptor comprising a conductive substrate having a surface shape in which the ratio of the height of the peaks to the depth of the valleys in a ruggedness pattern obtained from its filtering waviness curve is greater than or equal to a specific value, and the distance between adjacent peaks and the difference in level between adjacent peaks and valleys are within specific ranges.
As discussed above, there have been a variety of proposals for improving the surface shapes of photoreceptors in order to prevent blade curling, but these conventional techniques have all been unsatisfactory in terms of production cost because they require post-processing after formation of the photoreceptor or the introduction of specialized equipment.